Dietary Choline Supplements, but Not Eggs, Raise Fasting TMAO Levels in Participants with Normal Renal Function: A Randomized Clinical Trial

Abstract

Background: Choline is a dietary precursor to the gut microbial generation of the prothrombotic and proatherogenic metabolite trimethylamine-N-oxide (TMAO). Eggs are rich in choline, yet the impact of habitual egg consumption on TMAO levels and platelet function in human subjects remains unclear.

Methods: Healthy volunteers (41% male, 81% Caucasian, median age 28 years) with normal renal function (estimated glomerular filtration rate >60) were recruited and assigned to 1 of 5 daily interventions for 4 weeks: 1) hardboiled eggs (n = 18); 2) choline bitartrate supplements (n = 20); 3) hardboiled eggs + choline bitartrate supplements (n = 16); 4) egg whites + choline bitartrate supplements (n = 18); 5) phosphatidylcholine supplements (n = 10). Fasting blood and urine samples were collected for quantification of TMAO, its precursors, and platelet aggregometry.

Results: Participants' plasma TMAO levels increased significantly in all 3 intervention arms containing choline bitartrate (all P < .0001), but daily ingestion of 4 large eggs (P = .28) or phosphatidylcholine supplements (P = .27) failed to increase plasma TMAO levels. Platelet reactivity also significantly increased in the 3 intervention arms containing choline bitartrate (all P < .01), but not with eggs (P = .10) or phosphatidylcholine supplements (P = .79).

Conclusions: Despite high choline content in egg yolks, healthy participants consuming 4 eggs daily showed no significant increase in TMAO or platelet reactivity. However, choline bitartrate supplements providing comparable total choline raised both TMAO and platelet reactivity, demonstrating that the form and source of dietary choline differentially contributes to systemic TMAO levels and platelet responsiveness.

Trial registration: ClinicalTrials.gov NCT03039023.

Keywords: Choline; Eggs; TMAO.

Conflict of interest statement

Conflict of Interest Disclosures:

SLH reports being named as co-inventor on pending and issued patents held by the Cleveland Clinic relating to cardiovascular diagnostics and therapeutics, being a paid consultant for Procter & Gamble, and having received research funds from Procter & Gamble, and Roche Diagnostics. SLH also reports being eligible to receive royalty payments for inventions or discoveries related to cardiovascular diagnostics or therapeutics from Cleveland Heart Lab and Procter & Gamble. WT served as a paid consultant for Sequana Medical AG and received honoraria from Springer Nature and American Board of Internal Medicine, all unrelated to the present topic. The other authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Copyright © 2021 Elsevier Inc. All rights reserved.

Figures

Figure 1:. Study Design.

Participants were randomly assigned to one of five different intervention arms. All interventions provided a roughly equivalent dose of choline with the exception of Arm 3, which, as a combination of Arms 1 and 2, provided approximately twice as much choline as the other four arms.

Figure 2:. TMAO Concentration across Study Arms.

Comparing plasma TMAO concentration (uM) across all arms between the baseline (no intervention) visit and the final (intervention) visit, TMAO increased in the three arms involving the ingestion of a choline bitartrate tablet, but failed to show a significant increase when participants consumed only eggs or only phosphatidylcholine capsules (the two groups of participants that did not consume the choline bitartrate tablets). In this graph, the box indicates the 25th – 75th percentiles, with the solid line inside the box at the median. Each open circle represents an individual TMAO value. BL = Baseline, D28 = Day 28 (final study visit). P values were calculated with the Wilcoxon signed rank test, with values less than 0.05 deemed significant.

Figure 3:. TMAO Production across Study Arms.

A. Comparing the baseline visit and the final (Day 28) visit, 24-hour urine TMAO increased when participants consumed oral choline bitartrate tablets (either alone or in combination with eggs), but did not increase in the two arms where participants did not consume oral choline bitartrate tablets. B. A similar pattern was observed in spot urine. In this graph, the box indicates the 25th – 75th percentiles, with the solid line inside the box at the median. Each open circle represents an individual TMAO value. BL = Baseline, D28 = Day 28 (final study visit). P values were calculated with the Wilcoxon signed rank test, with values less than 0.05 deemed significant.

Figure 4:. Platelet Aggregation across Study Arms.

A. Comparison of platelet aggregation in 10 subjects between the baseline visit and the final (Day 28) visit, shown as measured aggregation in response to submaximal (1uM) ADP across all study arms in plasma. The box indicates the 25th – 75th percentiles, with the solid line inside the box at the median. B. Correlation between platelet responsiveness (as monitored by platelet aggregometry elicited by 1 μM ADP as agonist) and plasma TMAO concentration. C.Correlation between platelet responsiveness (as monitored by platelet aggregometry elicited by 1 μM ADP as agonist) and 24-hour urine TMAO levels. Spearman rank correlation and p values are also shown. BL = Baseline, D28 = Day 28 (final study visit).